In the prior art, discrete pointing devices such as a mouse or trackball are used to input cursor displacement information. Such input devices sense displacement, for example changes in orthogonal directions (X,Y), which in turn is used to reposition a cursor on the display screen. Discrete pointing devices are ergonomically deficient in that their use requires a user to move his or her hand away from the usual typing position to begin a pointing operation. Additionally, prior art devices fail to provide good cursor speed control.
U.S. Pat. No. 4,680,577 describes a multipurpose cursor control keyswitch which may be used in a keyboard as both a keyswitch (or typing device) to acquire typing (alphanumeric) data and as a pointing device to acquire pointing (direction) data. That patent discloses sensors coupled to the keycap to detect lateral forces applied to the keycap by a user. Ser. No. 07/557,546 discloses multipurpose keyswitches, i.e. keyswitches that include integrated force sensors for acquiring pointing data responsive to both lateral and vertical forces applied to a keycap, so that a user can enter both typing and pointing data at the same keycap.
Commonly-owned application Ser. No. 07/649,711 discloses a typing and pointing system, as indicated by the title, which automatically switches between a typing mode of operation and a pointing mode of operation, responsive to the user's actions, and without requiring an explicit user command to initiate the mode change.
Acquisition of typing and pointing data from the keyboard in an integrated or multi-function keyboard system, in a manner transparent to application software, is disclosed in commonly-owned application Ser. No. 07/672,641.
One problem in pointing systems in general is overshoot, i.e. moving a cursor beyond the destination intended by the user. Many pointing systems seemtoo fast when the user wants slow, careful pointing and, conversely, seem too slow when the user wants to move the cursor quickly, for example over several inches.